@supports

The @supportsCSSat-rule lets you specify declarations that depend on a browser's support for one or more specific CSS features. This is called a feature query. The rule may be placed at the top level of your code or nested inside any other conditional group at-rule.

@supports (display: grid) {
div {
display: grid;
}
}

@supports not (display: grid) {
div {
float: right;
}
}

In JavaScript, @supports can be accessed via the CSS object model interface CSSSupportsRule.

Syntax

The @supports at-rule associates a block of statements with a supports condition. The supports condition consists of one or more name-value pairs combined by conjunctions (and), disjunctions (or), and/or negations (not). Precedence of operators can be defined with parentheses.

Declaration syntax

The most basic supports condition is a simple declaration (a property name followed by a value, separated by a colon). The declaration must be surrounded by parentheses. The following example returns true if the browser's transform-origin property considers 5% 5% valid:

@supports (transform-origin: 5% 5%) {}

Function syntax

The second basic supports condition is a supports function, the syntax for these is supported by all browsers, but the functions themselves are still being standardized.

selector()

Tests if the browser supports the tested selector syntax. The following example returns true if the browser supports the child combinator:

@supports selector(A > B) {}

The not operator

The not operator can precede any expression to create a new expression, resulting in the negation of the original one. The following example returns true if the browser's transform-origin property doesn't consider 10em 10em 10em valid:

@supports not (transform-origin: 10em 10em 10em) {}

As with any operator, the not operator can be applied to a declaration of any complexity. The following examples are both valid:

Note: There is no need to enclose the not operator between two parentheses at the top level. To combine it with other operators, like and and or, the parentheses are required.

The and operator

The and operator creates a new expression from the conjunction of two shorter expressions. It returns true only if both of the shorter expressions are also true. The following example returns true if and only if the two shorter expressions are simultaneously true:

@supports (display: table-cell) and (display: list-item) {}

Multiple conjunctions can be juxtaposed without the need of more parentheses. The following are both equivalent:

The or operator

The or operator creates a new expression from the disjunction of two shorter expressions. It returns true if one or both of the shorter expressions is also true. The following example returns true if at least one of the two shorter expressions is true: